1. Technical Field
The present disclosure relates to a substrate, and more particularly to a substrate for fingerprint contact.
2. Related Art
Identity recognition plays an important role as a goalkeeper in the state security, enterprise information management and home security. Biometrics identifies and confirms the identity of a person according to specific physiological characteristics. Generally, biometrics mainly consists of recognition through voice, face, iris, vein, and fingerprint at present. Fingerprints are made up of many rough and uneven ridges and valleys. The fingerprints of each person are unique, a faint possibility exists that different persons have identical fingerprints, and the fingerprints are not likely to change as the age increases or health condition changes. Therefore, compared with other methods, fingerprint recognition is an easy and low-cost technology most widely used.
Conventional fingerprint recognition systems are mainly classified into optical, capacitive, ultrasonic, and thermal sensing fingerprint recognition systems. Briefly, an optical fingerprint recognition system acquires a greyscale digital image of the ridges and valleys of the finger by using an array including many Charge Coupled Devices (CCDs) through optical scanning. A capacitive fingerprint recognition system includes a sensing chip of a metal array. A surface of the chip is wrapped in an insulation layer. When a finger is placed on the sensing chip, different sensing capacitances appear, because the distance between a surface of the insulation layer and the metal array changes due to the ridges and valleys of the fingerprint. In an ultrasonic fingerprint recognition system, an ultrasonic signal is first transmitted into a finger, and then a pattern of the fingerprint is read from a reflected signal. When a corium laminar with high conductivity is detected in the ultrasonic signal, the ultrasonic signal is reflected to and read by the recognition system. A thermal sensing fingerprint recognition system measures a fingerprint pattern based on different thermal conductivities between an epidermis and the air.
A conventional optical fingerprint recognition system is a totally reflective optical fingerprint recognition system, mainly including an optical component and an optical imaging system. The optical component is used for reflecting and transmitting light through tools such as lenses, prisms and optical fibers, and the optical imaging system is mainly used for capturing an image of the fingerprint. One of the steps for fingerprint recognition is to emit light to the fingerprint of the finger at a preset angle first. Since the fingerprint is made up of the multiple rough, uneven and irregular ridges and valleys, when the finger contacts the optical component, the ridges contact the optical component, and the valleys do not contact the optical component. When the light irradiates the valley, the light is reflected in a chamber of the valley and is then emitted to the optical imaging system. Since the ridge directly contacts the optical component, when the light irradiates the ridge, the light is directly reflected, and is then emitted to the optical imaging system. In contrast to the case that the light irradiates the ridge, the reflected light of the valley generates a bright area, and the ridge generates a dark area, such that the fingerprint produces a clearly alternating bright and dark stripes pattern. According to the principle of optical total reflection, the light transmits the fingerprint to the optical imaging system to acquire an image of the fingerprint, and then the characteristics of each fingerprint are calculated and recorded according to the forms and details of the fingerprint by using an algorithm of the system. In this manner, fingerprint recognition is performed.
For the above-mentioned totally reflective optical fingerprint recognition system, the optical component guides the light to travel according to the principle of total reflection. Therefore, during the assembly of the optical fingerprint recognition system, the light incident angle and emergent angle of the optical component and the optical imaging system must be adjusted accurately, such that the light is effectively guided to be projected to the finger and reflected to the optical imaging system from the finger, and then the optical imaging system intercepts the image of the fingerprint pattern. Therefore, the assembly of the totally reflective optical fingerprint recognition system is difficult and complex, and the cost of the assembly is also high.
In addition, a light emitting element of the totally reflective optical fingerprint recognition system is a point light source, and if the light is not diffused through certain optical processing, the reflected light is likely to become non-uniform, resulting in an unclear image. Therefore, when capturing a fingerprint pattern of the finger, the totally reflective optical fingerprint recognition system may acquire a fuzzy image, resulting in a difficulty in fingerprint recognition.